When it comes to long life, NASA's Mars rover Opportunity takes after its robotic twin Spirit.

On Tuesday, Opportunity officially hit the one-year mark in its mission to explore Mars and send home data about the Red Planet's conditions and its history of water. The longevity of the two rovers — Spirit celebrated its own one-year anniversaryon Jan. 3 — has been a stunning success for rover scientists and engineers, who originally planned for just a 90-day mission.

"This whole mission has surpassed all of our expectations," said Steven Squyres, principal investigator for the rover mission at Cornell University.

Opportunity landed at Meridiani Planum at 12:05 a.m. ET on Jan. 25, 2004, though it was still late Jan. 24 at NASA's Jet Propulsion Laboratory in Pasadena, Calif., where the mission was being managed. Squyres said the entire rover team, including managers, engineers and scientists, planned a one-year celebration Monday night during a two-day mission science meeting at JPL.

But while Squyres said he looked forward to anniversary party, he is still waiting for Jan. 31. It was on that day in 2004 that Opportunity rolled off its landing platform and planted six wheels in Martian soil, he told Space.com.

"I've always felt that we had six terrifying events in this mission; two launches, two landings and two egresses," Squyres said. "And it wasn't until both [rovers] were in their native environments on Mars, for me, that I could really feel like I could breathe a sigh of relief."

Only a few major glitches have plagued Opportunity, including a stuck heater, which was a glutton for power early in the mission but circumvented later by the addition of a "deep sleep" mode during a software update. The rover's rear hazard-identification camera has also suffered some minor mottling in images due to dust picked up during recent investigations of its heat shield, JPL officials said.

A flood of science
Both Spirit and Opportunity have returned a wealth of data back to Earth, but rover scientists concur that Opportunity has made the lion's share of Mars science discoveries.

"When you look at the most important accomplishments of the mission, a lot of them were due to Opportunity," Squyres said. "It was the one that found the really powerful evidence for a habitable environment in Mars' past. It's sort have been the good-luck rover for this whole thing."

It was Opportunity's studies at its initial landing site Eagle Crater that gave scientists conclusive proof that the region had once been drenched in liquid water. Scientists now believe that Opportunity's Meridiani Planum landing zone supported a habitable environment and possibly a salty sea.

NASA / JPL / MSSS

A photo taken from orbit by NASA's Mars Global Surveyor shows Opportunity's landing site and its tracks through Meridiani Planum, ending at the rover itself, visible as a speck. The rover's landing platform also can be seen within Eagle Crater.

Matt Golombek, a rover scientist at JPL, spent years working to pinpoint Opportunity's landing site.

"There, we have been extraordinary," Golombek said in a telephone interview. "But we've only been able to look at a section of rock maybe 10 meters [33 feet] thick, and we want to know how do these rocks relate to what's above and beneath them."

Mars rocks have not been the only target for Opportunity's panoramic sights. The rover has also been able to swing by its own heat shield, which it cast off during the fiery entry into Mars' atmosphere. Opportunity's images and data taken of the scorched and twisted debris may help engineers develop better heat shields for future missions, NASA officials said.

The rover has also stumbled upon an iron meteorite, the first ever found on another world, which has galvanized rover and non-mission scientists alike to discuss its importance to their understanding of Mars. But for Squyres, just the fact that Opportunity has managed to move from Eagle Crater, to Endurance, to its heat shield and the meteorite is impressive.

"The value of mobility can't be overstated," he said of both Opportunity and Spirit. "We keep finding new stuff with both vehicles, and now this completely new and different-looking rock. No matter when this mission ends, there will still be something out there...that's one of the things I've had to come to terms with."

More exploration ahead
NASA officials have said the Mars rover mission is currently funded through March, with an average cost of about $3 million a month. But Spirit and Opportunity are in their second lifetime extension since the close of their respective 90-day mission in April 2004, and the prospect of another extension seems good so long as they continue to send home good data.

"There is certainly talk of getting another extension," Squyres said.

Rover handlers said that Opportunity, like its twin Spirit — which is busy crawling over hills at its Gusev Crater landing site — still has much to do. To date, the rover has driven 1.3 miles (2.3 kilometers), and engineers plan to send the rover toward a circular feature dubbed "Vostok."

A longer-term goal for the rover is the vast Victoria Crater, six times larger than Endurance, which lies across what researchers call "etched terrain" — a region they're not sure Opportunity will be able to pass through.

Practice run

Blastoff to Mars

A Delta 2 Heavy rocket lifts off from Cape Canaveral Air Force Station in Florida on July 7, 2003. The rocket launched the Opportunity rover toward Mars.
(Boeing via AP)
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Look at that!

Principal rover scientist Steve Squyres points at Martian snapshots displayed on a big screen at NASA's Jet Propulsion Laboratory, beamed back from the Red Planet just after the Spirit rover's landing on Jan. 3, 2004. NASA Administrator Sean O'Keefe, at right, and mission team members watch as the images are added.
(NASA)
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Leaving the nest

NASA's Spirit rover looks back at its own lander platform early Jan. 15, 2004, just after the mission team sent the robot out for its first spin on Martian soil. Spent air bags are crumpled along the sides of the platform. At the top of the image, the view is mirrored by the bottom of the rover's solar arrays.
(NASA / JPL)
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Rover's footprint

This image, taken by NASA's Opportunity rover and released Jan. 28, 2004, shows the "footprint" left by one of the rover's inflated air bags as the spacecraft bounced to its resting place on Martian soil. The circular region of the flowerlike feature is about the size of a basketball.
(NASA / JPL)
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In memoriam

NASA's Spirit rover took this picture of a plaque commemorating the fallen astronauts of the Columbia shuttle mission, which ended in disaster in February 2003. The 6-inch-wide plaque is mounted on the back of Spirit's high-gain antenna.
(NASA)
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RAT bites

This image, taken by the Opportunity rover on Feb. 28, 2004, shows two holes that allowed scientists to peer into Mars' wet past. The rover's Rock Abrasion Tool, or RAT, drilled the holes (indicated by red circles) into rocks in the region dubbed "El Capitan." An analysis of the drilled rock helped scientists determine that this part of Mars was once drenched in water.
(NASA / JPL)
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Bedrock beauty

A mosaic of images from NASA's Opportunity rover shows the rock region dubbed "El Capitan," which lies within a larger outcrop near the rover's landing site. The outcrop represents the first bedrock ever seen up close on Mars. This image was released March 2, 2004.
(NASA / JPL)
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Purple Planet

A false-color image from the Opportunity rover, released Feb. 9, 2004, accentuates the differences between a green-looking slab of Martian bedrock and orange-looking spheres of rock. Scientists likened the "spherules" to blueberries embedded within and scattered around muffins of bedrock. The spherules are thought to have been created by the percolation of mineral-laden water through the bedrock layers.
(NASA / JPL / Cornell)
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A scoop of berries

This microscopic image, taken at the outcrop region dubbed the "Berry Bowl" near the Opportunity rover's landing site, shows spherelike grains of rock or "blueberries." Of particular interest is the blueberry triplet, which indicates these geologic features grew in pre-existing wet sediments. This image was taken March 11, 2004.
(NASA / JPL / Cornell)
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A last look back

The "Lion King" panorama, captured by the Opportunity rover March 24 and 26, 2004, is a wide-angle view of Eagle Crater and the surrounding plains. Opportunity's landing platform is visible in the center, with tracks leading out of the crater.
(NASA / JPL / Cornell )
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Dunes of Mars

A false-color view from NASA's Opportunity rover, released Aug. 6, 2004, shows the dune field at the bottom of Endurance Crater. The bluish tint indicates the presence of hematite-containing spherules ("blueberries") that accumulate on the flat surfaces of the crater floor.
(NASA /JPL / Cornell )
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Wide-angle walls

NASA's Opportunity rover captured this view of "Burns Cliff" within Endurance Crater on Mars during the week of Nov. 13-20, 2004. The rover's solar arrays can be seen at the bottom of this true-color mosaic of 46 images. Because of the wide-angle view, the cliff walls appear to bulge out toward the camera. In reality, the walls form a gently curving, continuous surface.
(NASA / JPL)
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Martian clouds

Clouds add drama to the sky above Endurance Crater in this mosaic of frames taken by the navigation camera on NASA's Opportunity rover on the morning of Nov. 16, 2004. The view spans an arc from east on the left to the southwest on the right. These clouds are part of a band that forms near the equator when Mars is near the part of its orbit that is farthest from the sun.
(NASA / JPL)
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Farewell to Endurance

After spending six months studying rocks inside Endurance Crater, NASA's Opportunity rover climbed out Dec. 12, 2004, and used its front hazard-avoidance camera to look back across the stadium-sized crater from the rim.
(NASA / JPL)
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Alien junkyard

NASA's Mars Exploration Rover Opportunity gained this view of its own heat shield during the rover's 325th martian day (Dec. 22, 2004). The main structure from the successfully used shield is to the far left. Additional fragments of the heat shield lie in the upper center of the image. The heat shield's impact mark is visible just above and to the right of the foreground shadow of Opportunity's camera mast. This view is a mosaic of three images taken with the rover's navigation camera.
(NASA / JPL)
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Editor's note:
This image contains graphic content that some viewers may find disturbing.